Heating device



O. ZINGG HEATING DEVICE Filed Aug. 25. 1926 Patented Dec. 3, 1929 UNITED STATES PATENT OFFICE OSCAR ZINGG, OF BADEN, SWITZERLAND, ASSIGNOR Td AKTIENGESELLSCH AFT BROWN BOVERI 8t GIE., 0F BADEN, SWITZERLAND, A1JOINTSTOGK ZERLAND COMPANY, OF SWIT- HEATING DEVICE.

Application filed August 25, 1926, Serial No. 1

ports for the fluid to be heated.

Other and further objects will be pointed out or indicated hereinafter or will occur to one skilled in the art upon an understanding of the invention or its employment in practice.

In the drawing forming a part of this specification, I illustrate various arrangements wherein the invention may be embodied, but these are presented for purpose of illustration only and the claims are not to be regarded as limited simply to these.

In said drawing,

Fig. 1 is a longitudinal sectional view of' a tubular heating device containing an electrically heated coil;

Fig. 2 is a cross sectional view of same, the

section being taken on the line 22 in Fig 1;

Fig. 3 is a view similar to Fig. 1, showing a modified form of heating element; and

Fig. i is a view similar to Fig. 1, showing a further modified form.

When an electric heating splral is subjected to a stream of air directed chiefly along 1 its longitudinal axis, it usually occurs that the temperature of the spiral at the end where the cooled air enters will run lower than at the end where the heated'air leaves. This results in a rather inefiicient employment of the heating energy and gives rise to other undesired results. The present invention provides a construction whereby the movement of the air is accelerated as it passes along the spiral in such fashion that the velocity of the air relative to the individual turns of the spiral increases as it approaches tion at its ends to tunnel,

. creasing 31,335, and in. Germany September 17, 1925.

the outlet end. With this effect, the heating efiiciency of the spiral throughout its entire length is availed of to better advantage and overheating at the exit end is avoided.

In Fig. 1 is illustrated a heating device comprising a refractory tubular member 10 having a conical bore or tunnel of diameter d at the inlet endand diameter d at the outletend, and reference numeral 11 designatesa connection wherebyair is supplied to the tunnel at the inlet end. Within the tunnel of the tubular member are provided narrow radially extending ribs 12 tapering in height fromtheinlet to the outlet end so that their crests lie upon substantially the same radius from the axis of the tubular member, throughout their length. Upon these ribs is mounted the spiral -14 of resistance wire, which is arranged'forconnecelectric current. Air supplied to the inlet end of the tubular member, from the connection 11, at a suitable pressure, passes longitudinally through the tunnel of the former about and in contact with the heating spiral 14. Due to the tapering form of the tunnel, and also to the expansion of the air as it becomes heated, the rate of flow of the air increases as it passes through the spiral much more rapid flow than those at the inlet end. Consequently, there is a more nearly uniform transfer of heat from the spiral to the air throughout the entire length 8 of the former than is the case when the only acceleratlon of the air is that resulting from its expansion by the heat.

Fig. 3 shows a modified form in which the turns of the spiral 1a are t eo dlrectly on the walls of the conical bore of the tubularmember 10. In this arrangement the spiral is of tapering form so that a greater amount of heating surface is exposed by than those at the outlet end, the amount of heat transfer surface exposed per unit of length of the tubular member gradually defrom inlet to outlet. The tapering form of the tunnel in thisembodiment con-,

an appropriate source of 79 with the result that the turns of the at'the outlet end are subjected to a the turns adjacent the inlet end tributes to the acceleration of the flow of air through the element, as in the form first described.

.In the embodiment illustrated in Fig. 4 the tubular member 10 is of the form illustrated in Fig. 1, but the heating spiral -14-', while of uniform diameter from end to end,

has the pitch of the turns gradually increased from the inlet endto the outlet end.- This, accordingly, disposes more-heating surface in the larger portion of the tunnel Where the cold air enters, toward the outlet, and in conjunction with the accelerating effect of the conical tun nel, contributes to the rapid heating of the air and uniform extraction ofiheat from the spiral throughout its length.

Thus the invention contributes to efficiency by increase of outputof the heated fluid, more-uniform use ottheheating surface and avoidance of overheating ofthe element in any part.

WhatI claimis:

In a heatingdevice of'th'echaracter described, a casing member havinga passage extending from end-toend thereof,' the crosssectional area of such passage decreasing at a sub'stantially uniform rate from oneend of said casing memberto the other-end thereof, and a; heating element disposed'in such passage and being directlyengaged and sup,- po-rted by the material formingthe-interior surface portion of saidicasingemember.

In testimony whereof Ihave hereunto subfscribed myname at Zurich, Sivitzerland,this 9 day of August-,.A. D. 1926.

OSCAR ZINGG.

than in the portio11s-farther 

